1. Field of the Invention
The present invention is directed to a device for automatically receiving sheets in a pile at a delivery station of a sheet processing apparatus and for removing a complete pile of sheets from the processing machine, for example, a platen press.
2. Prior Art
In presently known platen presses, the processed sheets are delivered to a delivery station where they are accumulated in a pile on a pallet which is usually carried on a conveyor device that gradually lowers the pallet as the height of sheets deposited in the pile increases. When the pile of sheets reaches a given height, a retaining or interception device at the delivery station of the press, which device may be retractable fingers or retractable belts, is positioned to catch the sheets, which are continued to be deposited, as the pallet with the stack of sheets thereon is removed. The sheets held by the retaining device will build up into a pile, which has a rather low maximum height of about 10-15 cm, which height is determined by machine design considerations and the operational reliability of the sheet interception or retaining device. If the pile in the retaining device reaches the maximum height, a detecting device, which may be a photoelectric cell which checks the height of the piles of sheets in the retaining device, will cause the platen press to stop and thus interrupt production of the press. The full pallets are usually removed by means of a hand truck or lifter and then a new empty pallet is placed in the vertical conveying device to be raised to a position close to the sheet interception device to receive the sheets accumulated therein. When the new pallet is in the upper position, the interception device will retract and deposit the sheets accumulated thereon on the new pallet whereupon additional sheets conveyed to the delivery station of the press then accumulated on the new pile on the newly positioned pallet.
The above described delivery device does, however, have several drawbacks. For example, it cannot be unloaded quick enough when the platen press operates at a high speed and, therefore, the press is shut down or stopped due to exceeding an allowable height of the retained pile in the retaining or interception device. Therefore, all the advantages of the augmented operating speeds of the platen press are nullified by the frequent stops, which occur due to exceeding of the maximum height of the pile of sheets in the interception device during the removal of the full pallet.